Indirect effects of mammalian browsers on vegetation and ground-dwelling insects in an Alaskan floodplain

Abstract

Several studies in recent years have shown that large mammalian herbivores can have a substantial effect on boreal forest vegetation and soil dynamics. We studied the potential indirect effects of moose and snowshoe hare browsing on ground-living Orthoptera and Coleoptera and herb-layer vegetation in seven long-term exclosures and adjacent browsed plots. Insect and plant assemblages of exclosures and browsed plots differed from each other. Higher biomass of mosses, grass, and forbs characterized browsed plots, whereas Equisetum spp. and Pyrola asarifolia were more common in unbrowsed plots. Insect abundance was generally higher in browsed plots. Curculionidae was the only insect family that tended to be more abundant inside the exclosures. An enhanced food supply, in the form of feces and carrion of mammalian herbivores, and the direct and indirect effects of browsing on tree species composition, field-layer vegetation, litter, and microclimate are the probable causes of differences in the studied insect assemblages.